The present invention relates to a digital information signal recording apparatus and a digital information signal recording and reproducing apparatus, and in particular, to a digital information signal recording apparatus and a digital information signal recording and reproducing apparatus suitable for selecting and recording a plurality of video signals encoded into digital compression codes of different transmission rates and selecting and reproducing the recorded signals thereafter.
An example of a digital video tape recorder (VTR) in which a video signal is converted into a digital compression code for the recording and reproducing of the signal is described, for example, in two articles respectively in pages 588 to 596 and pages 597 to 605 of xe2x80x9cIEEE Transactions on Consumer Electronicsxe2x80x9d, Vol. 34, No. 3 (August 1988).
On the other hand, a digital broadcast is being put to practical use as a television (TV) broadcast of the next generation. For example, in the United States of America, there is known an advanced television (ATV) system in which a high-definition (HD) wide-band video signal having a resolution higher than that of a standard-definition (SD) video signal of the National Television System Committee (NTSC) system (525 lines/60 fields) or Phase Alteration Line (PAL) system (625 lines/50 fields) currently used is converted into a highly efficient digital compression code, thereby broadcasting the signal in the 6 megahertz (MHz) band-width presently used for TV broadcasting facilities. In addition, in association with the standard-definition system, there is known a system called xe2x80x9cDirect TVxe2x80x9d in which signals of a plurality of programs are converted into highly efficient digital compression codes respectively according to moving picture expert groups (MPEGs) such that the signals are transmitted via a satellite using time division multiplex communication.
In this situation, when these digital TV broadcasts are actually introduced to practical use, there are required digital VTRs corresponding thereto. However, in the prior art described above, consideration has not been given to technology for selecting and recording a plurality of digital TV signals of different transmission rates and selectively reproducing the signals thereafter.
An example of the apparatus in which a plurality of digital TV signals having different transmission rates are selectively recorded and reproduced is described in the U.S. Pat. No. 5,065,259 (corresponding to the JP-A-1-258255). This apparatus supports a plurality of recording modes such that information signals are encoded into digital data items of different transmission rates according to the recording modes. The encoded digital data items are then converted into signals of a fixed recording rate through a time-base or time-axis process. The obtained signals are recorded on a magnetic tape at a tape feed speed related to the transmission rates of the encoded digital data items, respectively.
However, in the apparatus of the U.S. Pat. No. 5,065,259, there has been missing technology associated with the automatic decisions of the recording modes in the signal reproduction process. Moreover, since an encoder is integrally included in the apparatus, consideration has not been given to the recording of such signals of digital data as digital video signals encoded in the MPEG system in which the transmission rate thereof varies with respect to time as well as for each of the programs, for example, programs of movies, sports, and news.
It is therefor an object of the present invention to provide a digital information recording apparatus and a digital information recording and reproducing apparatus for selecting and recording a plurality of digital video signals converted into digital compression codes having different transmission rates and selecting and reproducing the recorded signals, thereby solving the problem of the prior art.
To achieve the above object, a digital information recording and reproducing apparatus according to an aspect of the present invention comprises selecting means for selecting a signal to be recorded from a plurality of digital information signals having different transmission rates, identifier signal generator means for generating an identifier signal indicating contents of the selected signal, encoding means for conducting an interleaving process for the selected signal, forming blocks thereof by adding a synchronizing code, an identification code, an error correction code, and dummy data thereto, executing a time-base process and a modulation for the signal, thereby converting the signal into two channels of recording signals, recording and reproducing means including a first magnetic head and a second magnetic head respectively having azimuth angles respectively having opposing polarities and a third magnetic head and a fourth magnetic head opposing to the first and second magnetic heads with an angle of 180xc2x0, decoding means for conducting for a reproduction signal such decoding processes reverse to those of the encoding means as an equalizing process, a demodulating process, an error correcting process, and a deinterleaving process, thereby converting the reproduction signal into the original digital information signal, and servo means for controlling a rotation speed of a rotary drum and a feed speed of a magnetic tape.
When recording a first digital information signal in a range between a preset maximum transmission rate and one half thereof, the encoding means adds data such as dummy data thereto to convert the signal into two channels of recording signals having a fixed recording rate determined by the maximum transmission rate regardless of the input transmission rate, the servo means turns the rotary drum at a fixed rotation speed to feed the magnetic tape at a first feed speed, and the recording and reproducing means records and reproduces the two channels of recording signals on four tracks in one rotation of the rotary drum by alternately using the first and second magnetic heads and third and fourth magnetic heads.
On the other hand, when recording the second digital information signal in a range which is 1/N (N is an integer equal to or more than two) of that of the first digital information signal, the encoding means further compresses, each time the rotary drum makes N/2 rotations, the second digital information signal into a signal which is 1/N of the second digital information signal on a time axis, thereby converting the signal into two channels of recording signals respectively having the fixed recording rates, the servo means turns the rotary drum at the fixed rotary speed to feed the magnetic tape at a second feed speed equal to 1/N of the first feed speed, and the recording and reproducing means records and reproduces the two channels of recording signals on four tracks in one rotation of the rotary drum by using only the first and second magnetic heads or by alternately using the first and second magnetic heads and third and fourth magnetic heads. In this situation, the identifier signal indicating the contents of the recorded signal is also recorded as one of the identification (ID) codes together with the digital information signals.
The signals-reproduced by the first and second magnetic heads and/or the third and fourth magnetic heads are subjected in the decoding means to such processes reverse to those of the encoding means as equalization, demodulation, error correction, and deinterleaving so as to be converted into the original first or second digital information signal. In this operation, the decoding means detects the identifier signal thus recorded to control the time-axis process of its own and outputs to the servo means a reference signal to control the tape feed speed. On receiving the signal, the servo means sets the feed speed to the first or second speed employed in the signal recording operation.